


The Soul Mark

by Raithwin



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), Character Death, M/M, Sans/Doggo, Smut
Language: English
Status: Completed
Published: 2019-07-29
Updated: 2019-07-29
Packaged: 2020-07-25 01:48:46
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,356
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20024551
Author URL: https://archiveofourown.org/users/Raithwin/pseuds/Raithwin
Summary: Its not like anyone's ever died from doggy style, right? Red has needs, damn it.





	The Soul Mark

**Author's Note:**

> This weirdness arrived all at once late one night so now you all get to enjoy!

Sans _snarled_ as he angrily shoved aside the basket full of mustard drenched fries. He was fucking hungry as hell and these just weren’t satisfying that gnawing hunger at all. He hated when this happened! Hated that his beloved condiment snack only made him hungrier. He just wanted that void filled, damn it. Not only was it making him extra tired, the lack of energy was making him extra irritable to boot. It didn’t help in the least that the Boss had to go on some stupid ambassador trip across the freaking country.

The thought of Papyrus had Sans clutching at the three short links dangling from his collar. Damn it! Why the hell hadn’t he… Sans had texted him! He just needed a few moments of stars-be-damned attention. He needed something to take the edge off his _hunger_. Papyrus wasn’t supposed to be gone this long! He was supposed to be gone for two weeks, not five! Five weeks was long past the point when monster food didn’t give him the magic he needed. If Papyrus would just…

Someone plunked down on the stool next to Sans and leaned in close.

“Damn, bitch. What’s got you so pissy? Need someone to yank your chain?”

Sans glared at Doggo from the corner of a socket. The asshole seemed to have better sight when he wasn’t smoking his way through a bag of dog treats and one of his favorite hobbies was riling Sans up. And like all dogs, the mutt was really driven by what his nose told him. There was the tempting idea to shove the unappetizing plate of fries in Doggo’s face. The mustard would be really painful up that twitching canine nose. Simply the thought of it had Sans’s grinning wider.

“boss just likes ta keep me on a short leash, dickwad,” he snapped.

Doggo snorted, “Real damned short.”

Doggo’s paw shot forward and grabbed the bottom two links, yanking Sans closer. Sans growled and resisted, his sharp distal phalanges leaving deep scratches in the wooden bar top. Good thing this place wasn’t Grillby’s or Sans would been under _fire_ for doing that even if it was Doggo’s fault. Sans let himself have a mental laugh at the little joke.

“I’ve seen the way you react when Papyrus does this,” Doggo said in a low drawl, pulling harder, “But it ain’t always got this chain. I’ve seen a tag and nothing at all. Mean something, bitch?”

Sans had to bite back a small gasp at the sharp pull. The rough pressure on his cervical vertebrae had shivers running all through him. But he wasn’t about to give Doggo the satisfaction of seeing him react. If it was Papyrus here tugging on his leash he wouldn’t have to hold back. At least, not as much. Paps knew just how to get Sans quivering and eager with only a few words or actions. A tight grip and a huskily whispered promise never failed to excite him.

Just the idea of it, the phantom image of his Boss pulling him close and promising a good, hard fuck had Sans panting softly. His magic, which had already been low and eager for days, throbbed and tingled in response to the thought. Oh, he wanted it. _Hungered_ for it. But he couldn’t _have it_! And if he couldn’t have what he needed, he could at least start a fight. That might take the damned edge off. He could see the way Doggo was sniffing closer in interest to the spike in scents coming off him. That would make a fine fucking excuse.

Grinning nastily, Sans eyelight started to trail wisps of red magic, “as a matter of fact…”

A sudden snap of magic cut off his taunt. Doggo grunted in mild surprise as the chain he’d been holding vanished. The ring was left empty, as if nothing had ever been there. Sans pulled back a little as his expression morphed into a challenging leer.

_‘thank you, boss!’_ he thought gleefully.

“The hell’s that trick mean?” Doggo growled suspiciously.

He could probably smell how Sans’s excitement had spiked again.

“means I got free rein, horn-dog,” Sans purred.

Doggo blinked at him for a moment before a lustful sneer spread across his muzzle.

“You don’t say. I’d be glad to show you what its like to be a _real_ dog bitch, in that case,” he rumbled lowly.

He was probably trying to get Sans’s magic stirred up and excited with that low domination promise. Too bad for him that wasn’t what was exciting Sans. He _was_ interested in some hard sex though and he would bet G to spider donuts that a horny dog monster wouldn’t notice the difference. It wasn’t like the times the Boss decided to be cruel and tease him secretly in public. Manifesting magic tendrils inside Sans’s clothes to rub and tease him in the most arousing ways, but not _doing_ anything. Then, when Papyrus would finally relent and _fuck_ him…

Sans practically drooled at the memory. His pussy certainly did. It fluttered and clenched, sending painfully arousing tingles shooting up through him as magical fluid began to soak his shorts. He didn’t wear underwear. Too damned many layers.

“Smells like you like the idea, little bitch,” Doggo growled, leaning closer.

It brought Sans’s attention back to the present and he snarked back.

“maybe if you can back up those words, treat smoker.”

Doggo snarled and threw money on the counter as he shot to his feet.

“See if you can keep up, lazy ass.”

Sans knew Doggo hate the implication that his addiction impaired his oh-so-amazing prowess. Sans honestly couldn’t care one way or the other. The goal was to get the monster riled up and pissing him off was the way Sans knew best. They hadn’t spent years as antagonistic work neighbors for nothing after all. So Sans wasn’t surprised this time when Doggo grabbed for him. A quick shortcut had him off the bar stool and out of reach of the horny, irritated dog. Doggo’s paw closed on the air where Sans’s neck had been.

“uh uhh, no more collar play for you. i’ll let ya try to leave an impression though. i know a shortcut if yer feeling lucky, buddy.”

With one last challenging smirk, Sans turned and walked to the door. Heavy boots immediately followed him. Hook cast and set. He was getting god damned laid tonight. It wasn’t the Boss, but beggars can’t be choosers. And he had begged Papyrus pretty hard.

Opening the door, he magically twisted the fabric of reality around them. It created a dark tunnel that, after a dozen paces, dumped them into a dimly lit room Sans knew all too well. Doggo let out a stifled yelp.

“The fuck was that? Where are we?” he demanded.

Sans tsked irritably, “a short cut, ya sissy. to my room. or did ya need the walk ta build up confidence?”

He kicked off his untied sneakers before plunking down on his mattress and stripping off his shorts, revealing his eager, glowing ecto-pussy. Damn it, he was so fucking ready for some dick. The gnawing hunger was pushing him on hard. It was combining with and fanning the flames of his excitement in an ever building need. The Boss wouldn’t have even given Sans the chance to sit down. He knew exactly what and how Sans needed it when he got like this. He would of had Sans shoved up against the wall, pounding into him, making him scream in pleasure as he clawed more furrows in the boards. It had happened on more than one occasion.

Moaning at the thought, Sans fingers quickly found their way to his clit. He pressed hard, circling the nub and sending pleasure out in jolting spiked across his pelvis. Why wasn’t that mutt _doing_ anything yet?! A particularly strong tingle made him shutter in pleasure as he glared up at Doggo. He found the monster staring back hard, watching his every move with a decently sized tent in his pants.

“you gonna do something with that or just watch all night, fluff brain?!” Sans snapped.

If this fucker cowered out on him, Sans vowed to spread several nasty rumors about his lack of abilities in the sack. Right after pinning him down and _taking_ what he needed. He was hungry, horny, and had permission he wasn’t about to waste. Luckily for Doggo’s reputation, he snapped out of his trance and stalked forward with a growl.

“You better not need some damned foreplay,” he growled.

“doubt you’d be much good at it anyways,” Sans jeered back.

Even if the dog was any good with his tongue, he’d have nothing on the Boss. Papyrus had such beautifully fine control over his magic that he’d eaten Sans out with anywhere from one to three gloriously long, hot tongues. For hours. He would make Sans cry out and beg to be properly fucked, beg for more, harder, until Sans came screaming into Papyrus’s mouth. Only then would the Boss take his pleasure. And _take it_ he would.

_‘Shit!’_

He could get off just thinking about it, but that wouldn’t do anything about the damned hunger.

“Shut the fuck up and get on all fours, bitch,” Doggo snarled, yanking down his zipper.

Sans smirked as a pulsing, pointed cock sprang free. Here’s hoping there was a decent knot to go with it. He wanted something satisfying, not just pleasantly enjoyable. He felt like the damned Void inside. He wanted to be filled. Ravished with a savage energy that would leave him properly sated for the first time in weeks.

Rolling to his hands and knees, he was rewarded with the feel of Doggo settling behind him. Paws grabbed the crest of his ilia, claws scraping none to gently and sending tingles of painful pleasure zipping through him. A growl was his only warning. He just barely felt the hot tip catch against his puffy, wet lips before he was pulled back roughly to meet Doggo’s sharp thrust. All at once, that entire hard cock was buried inside him. A strangled cry wrenched itself from his throat as his pussy clamped down on the sudden fullness.

Well shit, this might be worth it after all.

“Take it, bitch!” Doggo snapped at him.

He pulled out nearly to the tip before slamming back in again, making Sans moan loudly, and set up an absolutely brutal pace right from the get go that had Sans’s core throbbing madly with bliss. _Oh,_ _hell yeah!_ That was what he needed! He could tune Doggo’s voice out easily enough. The deliciously hard, fast thrusts were all he needed to focus on. The way he was filled to the hilt each time. The vigorous energy he was being fucked with.

Sans let his skull drop to the mattress, tongue lolling out from between his jagged teeth. It didn’t take much prompting for his imagination to plaster an image of Papyrus over Doggo. Yeah, the dog monster’s cock didn’t have that magical tingling heat that added that perfect something extra, but Sans was familiar enough with it to pretend. Not everyone could be as amazing as the Boss after all.

In his mind’s eye, Papyrus smirked down at him and told him what a good bitch he was being. How well he was taking his Boss. That if he was good, he’d get something _especially delicious_ for the second round. A loud moan broke through the gasps and pants as his cunt quivered in excitement, clenching tighter around the cock pounding into him.

“ohhhhhhh, f-fuck…booooooosssss!”

“Tsk, you…better mean, nghh, me, bitch,” Doggo growled warningly.

Sans ignored him completely. Words tumbled from his mouth as he rocked eagerly into the barrage of thrusts.

“boss, boss, fu-uuuck! more! harder!”

His eyelights hazed with pleasure as the image of Papyrus he conjured gave an irritated little snarl. His hips were dragged up higher and Papyrus hunched over him, pace turning hard and deep, making Sans scream in pleasure.

“YEAH! yeeaaaa-aah!”

He could feel a knot starting to catch and pull at his entrance. It would just slip free of his eager pussy to rub against his sensitive lips before thrusting back in hard. And every time, Sans’s hard clit would be dragged more and more mercilessly against the growing knot. It was making him shake, bones starting to rattle faintly as more and more of those hard touches wound him up and pushed him towards that glorious, needed release.

“boooossss! Boss, pa-aahhhh~ please! N-neeEED it!”

The begging mantra tumbled out of him. He couldn’t rock back anymore. He was being held too firmly and the thrusts were coming too fast.

_“Touch yourself, Sans. Show me how much you need it.”_

“oh, fuuuck, b-boss! Nnuuh!”

The command sent a bolt of pleasure racing down to his pussy faster than his own hand. It pulled a rough, gasping moan from him as his fingers rubbed hard against his clit, trying desperately to match the rhythm being pounded against his pelvis. So close! He was so damned close! The knot was too big to pull out now. It dragged with blissful soreness back and forth along his sensitive walls. He just needed a little more!

The knot suddenly stilled as hot cum started to fill him in spurt after watery spurt accompanied by a triumphant howl that quickly became a startled yelp.

Triple cursed, star fucking, damn it! He’d been so fucking close! The conjured image of his Boss shattered and left him with the less appealing reality. Doggo had almost lived up to his fucking promise but now Sans was left mostly unsatisfied, wall still quivering, teetering slowly back away from the edge of an orgasm. As much as he enjoyed the feeling of being filled, his Boss was the only person who’d even made him come from it.

There was one enjoyable part at least. That irritating, painful, gnawing hunger was starting to abate. Each spurt of magically charged cum was another filling drop towards sating it. But it wasn’t enough. Papyrus had been gone for over a month now. And Doggo here didn’t boast the Boss’s near endless stamina or his deliciously concentrated magic. Fine, he’d just have to do it the old fashioned way.

He waited, panting and impatient, for Doggo to finish. Best to try not wasting any when the magic offered was this low. Or at least, that was the idea before Doggo slumped onto him as his release started to dwindle. What did this cocky asshole think he was doing?! With a snarl, Sans forced his summoned magic briefly, painfully, back into an intangible swirl. He couldn’t dismiss it fully, not as hungry and horny as he was, but it was enough to let him pull off Doggo’s knot and cock.

Before Doggo could do more than open his muzzle to protest, Sans snatched him up with gravity magic and flung him down onto the carpet. Sans quickly shortcut from the bed to straddling the dog’s chest where he shoved Doggo’s paws above his head. A blue bone attack went through each of Doggo’s wrists and his hands. More went through Doggo’s lower legs effectively pinning him in place. Doggo knew what those bones meant. Could even see them because the magical energy made them vibrate in such a way to be visible to the dog. Sans grabbed Doggo’s muzzle before he could make a bark of protest.

“ya didn’t back up that promise, smoke fer brains,” Sans growled down at him, “so you better get me off with that tongue of yours, capiche?”

Doggo, eyes narrowed, growled; pointedly showing his fangs as best he could. Sans growled back, showing off most of his own shark-like teeth.

“nice try, ya little shit. either you get me off, or you lose your limbs,” Sans promised darkly.

He summoned more blue bones to either side of the ones already piercing Doggo’s arms and legs, a silent guarantee to shred them if Doggo didn’t comply. Doggo, perhaps cowed by the fierceness in Sans’s voice, relented. Sans sneered down at him before moving to kneel over Doggo’s muzzle.

“get licking, dog. yer supposed ta be good at that,” Sans ordered tauntingly.

Then he let go of Doggo’s muzzle. Immediately, Doggo opened his mouth wide and leaned up. His tongue was hot and firm as it swiped up along Sans’s dripping pussy. Sans groaned and let his head fall back as Doggo ended the lick by flicking the tip of his tongue hard across his tingling clit. That felt fucking nice. Doggo repeated the action a few times, making Sans twitch and sigh blissfully. Doggo didn’t seem to be deterred by the fact that his own cum was slowly dripping from Sans’s still pulsing pussy into his mouth. Not that Sans really gave a flying fuck about how Doggo might feel about it so long as he kept that tongue moving.

“come on, do it proper, bitch,” Sans moaned, fingers digging into Doggo’s fur to pull the canine closer.

Doggo made an angry rumble. He pushed the next lick up into that eager cunt, making Sans gasp and then moan appreciatively. Soon, Sans was reduced to a quivering, bone rattling mass of pleasure as Doggo alternated between deep, long licks and rapid flicks against his swollen clit.

“that’s it, yeeeaaaaaah. shit, yes, th…naaah~ that’s it, bitch! juuuust like that.”

Doggo still had nothing on the Boss when it came to raw skills, but Sans had to admit, the guy could still do a damned respectable job eating pussy. Ragged, panting breaths filled the room as Sans hunched more and more into Doggo’s quick, confident tongue lashing. A tongue lashing that was becoming more and more eager, licking harder and faster. He was close again. So close. He let go of Doggo’s fur with one hand and reached up under his shirt to start dragging his claws between and behind his lower ribs.

Yes! Yes!! That was it! So close!

“gonnnna…gann, ohhhh, FUCK yeahhhh! Goonnaaahhhh-AAHH!”

With a final loud shout, Sans came hard. His pussy clamped down on Doggo’s tongue, gushing red, glowing release into his mouth. Doggo swallowed almost on reflex what didn’t run down his cheeks. Sans shuttered through his orgasm, the pleasure buzzing in his bones. When he finally came down from the high a few minutes later, there was only one thing messing up his amazing post-orgasmic bliss. He still felt that gnawing hunger for more.

A whine had him looking down at his captive fuck buddy. Doggo had finally pulled his tongue back. His eyes had blown wide and glassy with a new, fierce lust. He was absentmindedly lapping up any of Sans’s release that he’d missed. Sans glanced over his shoulder and found that Doggo’s cock was a stiff, angry purple and looked bigger than before.

“hell yeah!” sans crowed.

Another round was exactly what he needed to try and sate his hunger. Or possibly three more with the pathetic amount of magic Doggo gave in each. Lifting himself on shaky legs, Sans moved eagerly down Doggo’s still form until he was straddling the dog monster’s hips. Hips that were rocking lightly as if seeking a warm, moist hole to sink into. Sans shivered and scrapped along his ribs under his shirt. This was perfect. He could keep Doggo like this until he was actually satisfied. There was more to coming in the idiot’s mouth than the fun of it after all. Kneeling again, Sans reached down to wrap his bony fingers around Doggo’s leaking cock.

“so, still wanna know the meaning behind the collar change?” he asked, starting to pump slowly.

“W-whaaa…?” Doggo tried to ask as a low groan escaped him.

“you asked earlier. still wanna know? i feel like sharin’,” Sans prompted.

Doggo whined and nodded dumbly as Sans teasingly ran his thumb firmly up the underside of his dick.

“see, thing is, boss knows i get hungry when he’s away. didn’t use ta be a problem, could get my magic fix from just about anyone.”

His hand picked up speed.

“now, if he’s gone too long, the hunger starts ta get to me. the chain reminds me ta keep myself under control. who hold my loyalty and shit like that.”

Sans paused here, unable to wait any longer. He angled Doggo’s cock up more and sank down on it with a drawn out moan.

“fuuuuuuucck yeah~ mmhhm…so, the chain dissappearin’s the boss’s way of giving permission ta get my energy fix elsewhere. He…”

Sans was interrupted by a sudden harsh electronica beat and vibrations that made him start. He gave a surprised, bit off groan as the movement rocked him forward against Doggo’s hips, rubbing his cock against Sans’s walls in a new, exciting way. Rocking back, he repeated the motion as he pulled his phone from his jacket pocket. He didn’t even need to see the caller ID to know who it was. It was even a video call. Grinning hugely, Sans quickly hit the answer button.

“heeeyya, boss~” he purred, seeing the monster he really wanted between his legs.

Papyrus smirked at him, “SANS. I PRESUME YOU FOUND SOMEONE TO SNACK ON?”

Sans licked his teeth, leering at Papyrus as if sheer will power would transport the monster into the room for real.

“sure did, boss. he ain’t as impressive as he, mhhmm… seems ta think though.”

Papyrus snorted, “I AM NOT SURPRISED. ESPECISLLY WHEN COMPARED TO THE GREAT PAPYRUS. WILL HE AT LEAST BE EOUGH TO SATISFY YOU?”

“That depenNNDS! OOohhh fuck!”

Sans train of thought derailed as Doggo thrust up into him hard. His eyes were still glassy with lust but there was a hard glint to them that seemed to suggest his took offense to Sans talking on the phone while he fucked. Sans had to brace himself with a hand against Doggo’s chest to keep from collapsing from the hard thrusts threatening to turn his bones to jelly as they hit that perfect spot repeatedly. Each one forced an eager pant from his open mouth, tongue peeking out between his teeth, hips snapping back to meet the thrusts greedily.

“DEPENDS ON WHAT, SANS? AS MUCH AS I ENJOY THIS WELL FUCKED EXPRESSION, I CANNOT STAY ON THE PHONE LONG,” Papyrus warned.

“s-soooryyy, boss. depeendss o-on if…if I can use hiiiM all up or… nnghh! or not,” Sans finally managed to get out. Then he grinned at Doggo, “say hi~”

His thumb managed to hit the flip camera button. Doggo’s face replaced his own on the screen next to Papyrus’s. Papyrus made a small noise of mild interest before studying Doggo in silence. Sans took the opportunity to let out the sounds he’d been holding back while he struggled to speak. Doggo made an attempt to snarl at the camera before he too went back to eager panting. It was impossible to thrust as hard as he was without moving his legs. There were constant small chips of hp being torn from his already slightly depleted health as his legs turned bloody around the blue bones.

“HIS SKILLS ARE DECENT, BUT NOT IRREPLACEABLE,” Papyrus said at length, “THIS SEEMS LIKE A BETTER USE FOR HIM. ENJOY THE SNACK, SANS. I WILL GIVE YOU A PROPER MEAL WHEN I RETURN.”

Sans moaned loudly, his pussy lighting up with quivering pleasure at the promise. The Boss could put so much magic into each fuck that it filled him up every time. Damn, he couldn’t wait.

“suuure thing, boss.”

There was a pun here, he knew it. Something about hot dogs? Before his thoroughly distracted mind could come up with the rest of it, the phone beeped and the call ended. Mentally shrugging and giving up on the pun for now, Sans tossed aside the phone and his jacket.

“sucks taaaahh be you…oohh~ Doggo. now, lets see if ya-ahh! do better thissss round,” Sans moaned, dismissing the bones.

Doggo wasted no time in flipping them and pounding into Sans as if it was the last fuck of his life. As if every thought had stripped away down to the instinct to fuck and breed the monster under him until he had nothing left. Which suited Sans just fucking fine.

\- - - - - - - - - - - - -

When Papyrus returned home nearly two days later, he found Sans in the shower, scrubbing the last flecks of grey dust from his bones. His tasty cunt was still summoned, though very little other magic remained to cloud it, and the steam of the shower was filling the room with his half-sated scent. Well, he had promised his brother a proper meal when he returned. And a leisurely shower sounded luxurious after the grueling end to the conference.

“IT IS NICE TO SEE YOU CLEANING UP AFTER YOURSELF FOR A CHANGE, SANS,” he commented, leaning against the shower entrance.

Sans jumped, “boss! you’re back! finally.”

“TELL ME ABOUT IT. THAT TOOK FAR LONGER THAN I PLANNED,” Papyrus groaned.

Sans grinned at him, “sounds rough, boss. why don’t you join me in here and let me ease some of that tension?”

Papyrus chuckled lowly and quickly divested himself. He tossed his clothes into a laundry basket nearby and stepped into the shower. The hot water felt glorious on his aching bones. Sweeping Sans up into his arms, he first pressed a soft skeleton kiss against his teeth, enjoying the soft magical spark. Sans hummed happily and wrapped his arms around Papyrus’s shoulders.

“mhmm…welcome him, pap,” he said softly.

“Glad To Be Home, Sans,” Papyrus replied, just a soft, “How Long Did Your Snack Last?”

Sans laughed, “longer than expected! He only dusted on me late last night. I’ll have you know I vacuumed and everything too, ya neat freak.”

“Oh, Really? After A Nap Probably.”

“hehe, maybe~ so do i get a reward or what?”

Sans was positively leering at him. Papyrus replied by pressing the shorter skeleton’s back against the wall of the shower and forcing a delicious moan from him as Papyrus’s cock bottomed out in Sans’s greedy, dripping pussy.

**Author's Note:**

> There might be more to this. It may be somewhat episodic, we'll see.
> 
> PS. I swear I'm working on 'Sleeping Dogs'!


End file.
